The present invention relates to a refrigerating apparatus, an air conditioner and a scroll compressor for compressing a gas such as an air, a nitrogen and the like.
Hereinafter, a description will be given, for example, of a motor-driven hermetic scroll compressor used for air conditioning and the like.
Conventionally, in scroll compressors, control is effected so as to make a pressure in a reservoir for storing a refrigerating machine oil within a vessel equal to a discharge pressure and to make a pressure in an intermediate pressure chamber constituted by an orbiting scroll and a frame equal to an intermediate pressure between a suction pressure and the discharge pressure. Further, control is effected so that pressure differences are respectively generated between the refrigerating machine oil reservoir and the intermediate pressure chamber and between the intermediate pressure chamber and an outside of a compression chamber (having a pressure equal to the suction pressure). Further, the structure is made such that a flow passage for flowing the refrigerating machine oil is provided in a crankshaft, an end of the flow passage is open to the refrigerating machine oil reservoir within the sealed vessel, another end thereof is open to an upper portion of an orbiting bearing, the refrigerating machine oil is flowed from the upper portion of the orbiting bearing to a lower portion, and then the refrigerating machine oil is flowed to the intermediate pressure chamber, whereby a lubrication is performed.
Further, it is structured such that within the intermediate pressure chamber, after a part of the refrigerating machine oil lubricates a sliding portion of an Oldham ring, it lubricates a sliding surface between a non-orbiting scroll and an orbiting scroll from an outer peripheral portion of a base plate of the orbiting scroll and flows into a suction pressure area of the compression chamber having a pressure lower than the intermediate pressure.
In order to lubricate bearings (a main bearing and an orbiting bearing) during a compressing operation, it is important to supply the refrigerating machine oil having a lubricating function. When the refrigerating machine oil is supplied to the bearing, an oil pressure is generated due to a wedge effect, and the bearing floats up from a crankshaft, thereby providing a lubricating aspect so called as a fluid lubrication. Further, in correspondence to an operating condition, a load applied to the bearing is increased and an oil film is made thin, so that the bearing and a rotary shaft are likely brought into contact with each other, thereby providing a lubricating aspect so called as a boundary lubrication.
When the lubricating state is changed from the fluid lubrication to the boundary lubrication, a coefficient of friction is widely increased, so that a frictional heat is generated between the bearing and the crankshaft. Accordingly, a viscosity of the refrigerating machine oil is lowered and the oil film is harder to be formed, so that a reliability of the bearing is significantly reduced. In order to secure a lubricating performance of the bearing, it is necessary not only to supply the refrigerating machine oil necessary for forming the wedge-shaped oil film but also to supply an oil amount necessary for removing a heat generated in the bearing by means of the refrigerating machine oil.
On the other hand, in view of a pressure distribution within the scroll compressor, since the outside of the compression chamber is a low pressure area, it is obvious that an oil and a gas in the other higher pressure areas easily flow thereinto.
Accordingly, all amount of the refrigerating machine oil supplied to the orbiting bearing flows into the compression chamber via the intermediate pressure chamber, however, it lubricates the Oldham ring in the intermediate pressure chamber, lubricates the sliding surface between the orbiting scroll and the non-orbiting scroll, and improves a sealing performance of the compression chamber.
On the contrary, in the case that an amount of the lubricating oil is excessive, when a side surface of a wrap of the orbiting scroll and a side surface of a wrap of the non-orbiting scroll move close to each other during an operation, the refrigerating machine oil at an amount more than a clearance set between the both surfaces exists, so that a power for displacing the refrigerating machine oil is required in a compressing process, whereby an input of the compressor is increased.
In a refrigerating cycle, a refrigerant is dissolved in the refrigerating machine oil supplied to the compression chamber. When the refrigerating machine oil is agitated in the intermediate pressure chamber by a balance weight, a refrigerant gas is discharged from the refrigerating machine oil. Therefore, the pressure of the intermediate pressure chamber is controlled to be higher than the suction pressure and lower than the discharge pressure, thereby releasing the refrigerant gas to a side of the compression chamber having a lower suction pressure.
Further, the refrigerant gas is also discharged from the refrigerating machine oil flowing into the compression chamber, the refrigerant gas is discharged from the compression chamber into the vessel so as to be again dissolved in the refrigerant machine oil, and is again sucked from the intermediate pressure chamber. That is, since the refrigerant is circulated within the compressor so as to be joined with the refrigerant gas sucked from the suction pipe and an amount of the refrigerant gas at which the compression chamber can suck from the suction pipe is reduced, a circulating amount of the refrigerant in the refrigerating cycle is reduced.
Further, the refrigerating machine oil is discharged from the compression chamber together with the refrigerant gas and discharged from the compressor in a mist state. As a result, the refrigerating machine oil attaches to an inner wall of an outdoor or an indoor heat exchanger, thereby reducing a heat transmitting performance thereof. Particularly, in the case that the heat exchanger is an evaporator, much time is required until the refrigerant in the refrigerating machine oil is completely discharged, an evaporating amount of the refrigerant which is liquefied in the refrigerating cycle is reduced, and a reduction of a refrigerating capacity is caused.
Further, a balance weight rotates within the intermediate pressure chamber, so that when the refrigerating machine oil is filled, a resistance due to agitating is increased and an electric power is increased.
In comparison with an oil amount necessary for lubricating the bearing and securing a reliability at a high load, an oil amount necessary for lubricating and sealing the compression chamber is widely a little, and generally, the oil amount is determined in preferential of the lubrication of the bearing and the reliability at the high load, however, a reliability and an electric power save are in a mutually opposed relation.
An object of the present invention is to provide a scroll compressor which can limit a flowing amount of a lubricating oil to a compression chamber even when supplying a lot of lubricating oil to a bearing so as to restrict a reduction of performance due to an excessive inlet flow and can well lubricate the bearing.
The object mentioned above can be achieved by a scroll compressor comprising: a vessel; a compressing mechanism provided within said vessel, the compressing mechanism comprising an orbiting scroll and a non-orbiting scroll each having a spiral wrap formed in a base plate and an Oldham ring for preventing the orbiting scroll from rotating around its axis; an oil reservoir provided within a vessel; a crankshaft for transmitting a power for compressing a working fluid; and a frame on which a main bearing for supporting the crankshaft is provided, wherein the crankshaft is provided with oil supply passages for communicating a vicinity of an orbiting bearing and a vicinity of the main bearing, and openings of the oil supply passages in the vicinity of the orbiting bearing and in the vicinity of the main bearing are positioned so that a pressure of an oil film in the orbiting bearing opening generated during an operation of the compressor is higher than a pressure of an oil film in the main bearing opening generated during an operation of the compressor.
In other words, it is achieved by utilizing a pressure difference between both bearing portions and discharging the lubricating oil flowing from the orbiting bearing and the main bearing to the compression chamber via the intermediate pressure chamber to the oil reservoir.